In an organic EL display panel in which organic EL elements are arranged in a matrix on a substrate, light emitted from organic EL elements is used as pixels to display an image.
An organic EL element has a structure in which a functional layer including a functional material, for example an organic light-emitting layer including an organic light-emitting material, is sandwiched between a pair of electrodes. Aside from an organic light-emitting layer, a functional layer may be a hole or electron injection layer, a hole or electron transport layer, a hole or electron blocking layer, a buffer layer, etc., the function of which may be determined by a functional material contained within and by a relationship with an adjacent layer.
Methods of forming such layers are broadly separated into dry processes such as vacuum deposition and wet processes such as inkjet printing. A wet process is a method using an ink in which a functional material is contained in an organic solvent, and when considering formation accuracy and cost of a functional layer, is regarded as a technique suitable for high resolution and large sizes of organic EL display panels. In particular, among wet processes, development is progressing in inkjet methods in which ink is ejected onto an application region where a functional layer is formed while a nozzle capable of ejecting ink as minute droplets is caused to scan along a top surface of the substrate (for example, see Patent Literature 1).
In such an inkjet method, a plurality of nozzles aligned in a row are used for production efficiency, but as resolution and size of display panels increase, the number of nozzles used reaches several tens of thousands. Among this large number of nozzles, adhesion of dried ink or foreign matter may generate defective nozzles for which ink application location or application amount deviates greatly from set values and for which correction is impossible. In the case of a defective nozzle, a supplementary method is used in which ink ejection from the defective nozzle is not performed, and an application amount from a neighboring nozzle is used instead. For example, there is a method of increasing the number of times ink is applied to the same application region by a nozzle adjacent to a defective nozzle (for example, see Patent Literature 2).